Electron emitting cathode



June 1 1947; E. A. COOMES ELECTRON EMITTING CATHODE Filed July 9, 1945 FIcsiI NIG KEL SLEEVE NICKEL MESH EMITTING OXIDE FILLING FIG. 2

INSULATING BLOCK FILAMENT VOLTAGE EMITTING OXIDE AND MESH E D O H T A C m E M A I F INVENTQR I EDWARD A. GOOMES ATTORNEY Patented June 17, 1947 2,422,469 7 ELECTRON EMITTING CATHODE Edward A. Gnomes, Cambridge, Mass, assignor, by mesne assignments, to the United States of America, as represented by the Secretary of War Application July 9, 1945, Serial No. 604,012

1 Claim.

My invention relates in general to thermionic tube structure and more particularly to an improved form of cathode therefor.

In apparatus such as radio object-locating apparatus it is necessary that pulses of extremely large instantaneous power and short duration be developed and due to the Voltage used and the currents involved, the life of tubes used in this type of apparatus has not been nearly as long as desirable, mainly because of the effective life of the cathode thereof. Accordingly, it is one of the main objects of my invention to provide a thermionic cathode which is particularly adaptable for use in this general type of tube and which will have along life.

The pulses hereinafter referred to necessitate a high primary emission from the cathode when such a tube is working under pulsed conditions. Therefore, it is another of the objects of my invention to provide a cathode which when used in tubes of this nature, will give a high primary emission.

Since the values of current involved are large, comparatively speaking, and since Voltages involved are considerable, it has been noted in the past that a certain amount of sparking will take place at the cathode and it is desirable that this sparking be minimized or if it occurs at all that the value of the current emitted by the cathode be as large as possible before this phenomenon takes place. It is, therefore, another of the objects of my invention to provide a cathode in which an increased value of current will be provided before sparking takes place as compared to those cathodes which have been utilized previously.

My invention will best be understood by reference to the drawings, in which:

Fig. 1 illustrates one embodiment thereof; and

Fig. 2 shows a modified form of the invention.

Referring to Fig. 1, there is shown a preferable form of cathode structure in accordance with my invention. In this figure a nickel sleeve II] has actually cover the wire mesh but is just thickv enough to fill in the gaps of the wire mesh. This results not only in an improved emitting mate rial but also results in a very good heat distribution throughout the emitting material and hence the thermal conductivity can be maintained substantially constant and the advantages of the described structure can be maximized.

Referring to Fig. 2, there is shown a crosssection of the structure with the usual type of heating filament and attendant insulating blocks used. In this figure, the nickel sleeve to holds the mesh [5 with the emitting oxide held in close contact thereto and each end of the sleeve contains an apertured insulating block 20 and through which is passed the leads to the heater element 25. The heater element is energized by a filament voltage from a source not shown, but indicated.

It will be obvious tothose skilled in the art that there may be departures from the particular showing herein which will fall fairly within the spirit and scope of the invention and accordingly I claim all such departures as fall within the purview of the hereinafter appended claim.

, WhatIclaim is:

A cathode comprising a metallic, unperforated tube, an uncoated metallic mesh surrounding the tube and metallically integrated therewith and comprising straight wires disposed at right angles to define rectangular spaces around the tube, electron emissive material at the bottom of each space and in contact with the metallic tube and the wires, the latter extending exposed beyond the outer surfaces of the electron-emissive material.

EDWARD A. COOMES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,946,603 Von Wedel Feb. 13, 1934 2,212,827 Etzrodt Aug. 27, 1940 2,147,447 Kolligs Feb. 14, 1939 2,273,763 Reerink et al Feb. 17, 1942 1,870,951 Fredenburgh Aug. 9, 1932 FOREIGN PATENTS Number Country Date 488,873 Great Britain Nov. 5, 19,37 

